Effects of substituted side‐chain position on donor–acceptor conjugated copolymers

Abstract

The optical properties and electrical properties of a series of low‐band‐gap conjugated copolymers, in which alkyl side chains were substituted at various positions, were investigated using donor–acceptor conjugated copolymers consisting of a cyclopentadithiophene derivative and dithienyl‐benzothiadiazole. With substituted side chains, the intrinsic properties of the copolymers were significantly altered by perturbations of the intramolecular charge transfer. The absorption of poly[2, 6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3,4‐b′]dithiophene)‐alt‐4, 7‐bis(4‐octyl‐thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [PCPDT‐ttOTBTOT (P2)], which assumed a tail–tail configuration, tended to blue shift relative to the absorption of poly[2,6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3,4‐b′]dithiophene)‐alt‐4,7‐bis (thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [PCPDT‐TBTT (P1)]. The absorption of poly[2,6‐(4,4‐bis(2‐octyl)‐4H‐cyclopenta‐[2,1‐b:3, 4‐b′]dithiophene)‐alt‐4,7‐bis(3‐octyl‐thiophene‐2‐yl)benzo‐2,1,3‐thiadiazole] [PCPDT‐hhOTBTOT (P3)], which assumed a head–head configuration, was blue shifted relative to that of P2. The electrical transport properties of field‐effect transistors were sensitive to the side chain position. The field‐effect mobility in P2 (μ2 = 1.8 × 10−3 cm2/V s) was slightly lower than that in P1 (μ1 = 4.9 × 10−3 cm2/V s). However, the mobility of P3 was very low (μ3 = 3.8 × 10−6 cm2/V s). Photoexcitation spectroscopy showed that the charge generation efficiency (shown in transient absorption spectra) and polaron pair mobility in P1 and P2 were higher than in P3, yielding P1 and P2 device performances that were better than the performance of devices based on P3. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A General Protocol for the Polycondensation of Thienyl N-Methyliminodiacetic Acid Boronate Esters To Form High Molecular Weight Copolymers

“…Using identical conditions to that successful for forming high molecular weight pCPDT-BT from 3 , pCPDT-TBTT was produced in excellent yield and high molecular weight (entry 3) with both being greater than those reported for polymers produced by Stille cross-coupling reactions (entry 4 is a representative example). 23 Therefore, this polymerization protocol using monomer 3 is applicable to copolymerization reactions with a range of electronically distinct dibromo comonomers. The importance of KOH as base in achieving appropriate slow release of the boronic acid again was confirmed using K 3 PO 4 as base instead of KOH under otherwise identical polymerization conditions.…”

Synthesis and characterization of new conjugated materials based on benzobisazoles and their incorporation into electronic devices

“…5,84 For CPs, there are a set number of repeat units referred to as the effective conjugation length that defines the point at which adding additional repeat units no longer affects the band structure of the material. [85][86][87] The HOMO and LUMO correspond to the top of the valence band and bottom of the conduction band, respectively. Assuming a repeat unit of (-CH-) x , these energy levels should converge to resemble the half-filled orbitals of metallic conductors, yet they do not.…”

Synthesis and Characterization of Dithieno[3,2-<I>b</I>:2′,3′-<I>d</I>]Thiophene-Based Copolymers for Polymer Solar Cells

“…[1][2][3][4][5][6] Significant efforts have been applied toward improving the power conversion efficiencies (PCEs) of PSCs. Many factors limit the performances of PSCs.…”